Aircraft in flight sometimes encounter icing conditions whereby ice accretes onto airframe components. If left unchallenged, ice accretion on airframe components severely degrades aircraft performance, for example, by degrading the aerodynamic characteristics of lift surfaces, disruption of engine air flow and blockage of cooling air inlets and the like. Therefore, aircraft certified for flight into known icing conditions will have its flight critical airframe components equipped with icing protection systems.
A variety of icing protection systems are known. For example, airframe components may be provided with electrical resistance heaters in the vicinity of likely ice accretion (usually the leading edge surfaces of an airframe component in flight) which serve to heat the airframe components so as to prevent ice formation and/or to allow already accreted ice to be shed. Alternatively (or additionally) icing protection fluid (typically an alcohol based fluid) can be sprayed or caused to flow onto airframe ice accretion regions so as to preclude ice formation.
Another form of an icing protection system that is usually found on turbine powered aircraft and is known colloquially as a “bleed air” system. Conventional anti-ice bleed air systems employ heated air that is taken from (bled) from the compressor section of the engine and ducted to airframe components in need of anti-ice protection, such as leading edges of the aircraft lift surfaces (i.e., so as to prevent degradation of aerodynamic properties), inlet lips of engine nacelles (i.e., so as to prevent blockage or loss of efficiency of engine combustion air inlets and/or ice shedding that can damage the engine), and the like.
Broadly, the subject matter disclosed herein provides for devices and methods which provide icing protection for aircraft air inlet scoops utilizing residual thermal energy from heated air discharged from an aircraft's primary bleed air icing protection system.
According to some embodiments, the invention provides aircraft air scoop icing protection systems having an air duct provided with air inlet and outlet openings, a fairing which covers the air duct and defines an interior fairing space in which at least a forward portion of the air duct is positioned, the fairing having a forward end which surrounds the air inlet of the air duct, a tube having an inlet end in communication with a heated air chamber associated with an airframe part of the aircraft (e.g., a chamber which receives primary bleed air from the aircraft's engine), and an outlet end in communication with the interior fairing space. As such, the heated air in the heated chamber, which has already served its primary purpose of providing anti-ice protection to the associated airframe part but which also has residual heat energy, is directed through the tube to the interior fairing space so as to provide icing protection to the air scoop. The fairing is preferably provided with a rearward discharge end to allow heated air introduced into the interior fairing space to be discharged therefrom.
The aircraft air scoop icing protection system may be comprised of a pair of tubes each having an inlet end in communication with a heated air chamber associated with an airframe structure of the aircraft and an outlet end in communication with the interior fairing space. The pair of tubes may be oriented so that the discharge ends are positioned laterally adjacent the air duct.
The icing protection system as disclosed herein is especially useful for providing icing protection to engine nacelle air scoops. Thus, according to other aspects of the invention, an engine nacelle is provided which comprises an inlet lip which defines a chamber for receiving heated bleed air, and an air inlet scoop adjacent the inlet lip which includes an icing protection system as disclosed herein. Specifically, it is preferred that the icing protection system will include an air duct having air inlet and outlet openings, a fairing which covers the air duct and defines an interior fairing space in which at least a forward portion of the air duct is positioned, the fairing having a forward end which surrounds the air inlet of the air duct, a tube having an inlet end in communication with the chamber of the inlet lip of the engine nacelle, and an outlet end in communication with the interior fairing space. In such an arrangement, heated air in the chamber is directed through the tube to the interior fairing space so as to provide icing protection to the air duct.
The engine nacelle may comprise a bleed air conduit positioned in the chamber of the inlet lip. The bleed air conduit will have apertures for directing heated engine bleed air against an interior surface of the inlet lip. The heated air will thus be contained within the chamber where it may be redirected via one or more tubes to the interior fairing space to allow its residual heat energy to provide icing protection to the air scoop.
According to other aspects of the invention, icing protection for an aircraft air scoop are provided by providing an air scoop having a fairing over a portion of an air inlet duct so as to define an interior fairing space, establishing fluid communication between a heated chamber associated with an airframe structure and the interior fairing space, and allowing heated air from the heated chamber to flow into the interior fairing space and thereby provide icing protection to the air scoop. Preferably, the step of establishing fluid communication between the heated chamber associated with an airframe structure and the interior fairing space is provided by one or more tubes extending therebetween.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.